In the context of skeletal tissue repair, Cell Therapy is the local application of autologous (host-derived) cells to promote reconstruction of tissue defects caused by trauma, disease or surgical procedures. The objective of the Cell Therapy approach is to deliver high densities of repair-competent cells to the defect site in a format that optimizes both initial wound mechanics and eventual neotissue production. Osiris Therapeutics, Inc. is a start-up company engaged in the development of cellular transplants and cell-matrix products for the treatment of soft tissue and bone disorders. These cellular transplants and cell-matrix products are derived from the isolation, purification and propagation of human Mesenchymal Stem Cells (MSCs), the progenitor cells which give rise to all mesodermal tissues such as cartilage, ligament, tendon and muscle. A Phase I program is proposed to: 1. Demonstrate the efficacy of a proprietary cell delivery concept for autologous MSC therapy in short-term rabbit Achilles tendon implants. 2. Develop appropriate surgical techniques and perform preliminary implants for the repair of defects of the rabbit anterior cruciate ligament.